Plating method



Patented Nov. 23, 1926.

UNITED STATES tsoazso PATENT orrica.

ROBERT JAY SHOEMAKER, OF CHICAGO, ILLINOIS, ASSIGNOR TO LEADIZING COMPANY,

- OF CHICAGO. ILLINOIS, A CORPORATION OEILLINOIS.

marine wise, with a body of plating metal in a m01-,

ten state to produce a like film or coating thereon, and then producing a further depo- 1 sition either of the same or of another plating metal by electrolytic action. I

The method is of particular utility in the plating of iron or steel articles with lead.. When anattempt is made to plate an iron or steel article with lead by electrolysis diffi-' culty is experienced in obtaining acoating which will be dense, smooth and permanently adherent. Due probably to the necessary lack of concentration of the electrolyte and the tendency of the same to react chemically with the iron the deposit of lead is spongy and uneven. A dense coating of lead can be obtained without the use of an electric current by means'of a highly concentrated solution of lead acetate, or by the immersion of the article in a lead bath, but in such case the coating will be thinner than is sometimes desirable. For example, it is hardly feasible to obtain in this way a coat ing of more than one and a half to two ounces per square foot y I have discovered, however, that if the article is first dipped into a solution of lead acetate, for example, or after suitable fluxing into a molten bath of lead (the former expedient being preferable for reasons of economy) and is then treated electrolytically a very dense, smooth, adherent plating may be obtained of any thickness desired. For example, the lead coating may be built up to a thickness of from sixto eight ounces per square foot. y

The firstlead plating operation may also be advantageously combined with a subsequent electro-plating of the article with cops lead and thenrwith copper a good substitute METHOD.-

1923. Serial No. 651,415.

for solid copper may be obtained at a very low cost; For silver plating the underlylng lead coating decreases cost by making possible a thinner plating of the plating metal. 7

In the place of lead vfor the first coating when the hot dipping'method. is employed, it/is possible touse mixtures of lead and tin,

orlead, tin-and antimony, or tin alone or mixed with'a small. amount of antimony.

The first plating operation may be accom-. plished by either-of: the following two methods: r

(1) The article is first cleaned in the usual manner by means of a suitable acid for the purpose of removing traces of rust or grease. It is then immersed in a concentrated water solution of lead acetate and acetic acid. The solution should contain, at

least 35% bylweight of lead acetate although,

to get the best results,the lead acetate content should be 40% to The acetic acid should not be less than 5%. The solution is heated. Otherwise theaction will be extremely slow. Preferably it is maintained of zinc chloride and 20% by weight of com mon salt and is supported in a confined area on the surfaceof the lead bath. The article is passed through'the flux into the lead.

bath which, latter is maintained ata temperature of approximately 700 Fahrenheit. After removal of the article from the bath it is washed.

With either of the above methods the article is covered with a dense: adherent film or coating o flead which, however,-may

'be thinner than is desirable.

Assuming that a thicker coating of lead is required, the article is then introduced into an electrolytic cell containing a 10% water solution of lead; acetate, or ,in place of the lead acetate solutiona 10% solution of lead silica-fluoride. Preferably I add to the electrolytea soluble distillate of an organic carbohydrate such for example, as a water soluble product of the dry distillateof wood,

known commonly as wood tar. The organic substance prevents treeing. The positive electrode is a body of lead, the article to be plated being connected with the negative form deposition of tie lead over the entire surface of the article. A weak current should be used, that is, a current of not more than one ampere per square foot of surface to be plated which may be later increased to two amperes. If too strong a current is used the plating will be spongy.

By this method the coating may be built up to any desired thickness and will be dense and have a smooth exterior surface. The original lead coatingobtained through chemical action in the first step of the process protects the iron from contact with the electrolyte, thereby preventing the chemical reaction between the iron and the electrolyte which would interfere with the proper deposition of the lead on the iron if an attempt were 'made to deposit the lead directly on the iron surface by electrolytic action.

- If it is desired to plate the article'with some other metal than lead, for example, with tin copper, nickel or silver, the artlcle after being lead coated in accordance with the first step of the method above described, that is, by immersion in the salt solution of lead or in a bath of molten lead, will be electro-plated with copper, tin, nickel or silver, as the case may be, using any of the ordinary electro-plating methods common for these operations. 1

This application is a continuation in part of my copending application Serial No. 397,179 filed July 19, 1920 as a division of application Serial No. 374,089 filed April 15, 1920 (pa-tented Jan. 31, 1922, as Patent I claim:

'1. Method of plating a metal article which consists in covering the article with a coating of lead, and then superposing on the 'coatin thus formed a second coating produced y electrol sis.

2. Method of p ating a metal article whic consists in covering the article with a coat-.

ing of lead and then superposing on the coating thus formed a second coating of lead produced by electrolysis.

3. Method of lating a metal article elec tropositive to eadwhich consists in first bringing the article into contact with a solution of lead acetate to produce a deposition of lead on the article, and then superposing on the coating thus formed a second metal vplatin produced by electrolysis.

4. fiet 0d of platin a metal article electropositive to lead w ich consists in first 6. Method of plating which consists in first bringing the article into contact with a solution of lead acetate having a concentration of at least 35% 'by weight, and then superposing on the lead coating thus'formed a second coating produced by electrolysis.

7. Method of plating which consists in first bringing the article into contact with a solution of lead acetate "having a concentration of at least 35% b weight and then superposing on the lea coating thus formed a second lead coating produced by electrolysis.

8. Method of lead plating an iron or steel article which consists in first bringing the same into contact with a concentrated solution of lead acetate without electric current, then subjecting the article to an electro-plating operation using a lead salt solution of lesser concentration as an electrolyte. 9. Method of lead platin an ironor'steel article which consists in first bringing the same into contact with a concentrated solution of lead acetate without electric curtro-plating operation using a lead salt solution of lesser concentration as an electrolyte,

and keeping the electrolyte in agitation.

10.. Method of lead plating an iron or steel article which consists .in first bringing the same into contact, without electric current, witlra solution of lead acetate 'havin a concentration of at least 35% by weig t, and

.then subjecting the article to an electro-plating operation using a/ lead salt solution havby weight. j

11. Method of lead plating an iron or steel article which consists in first bringing the. same into contact, without electric current,

with a solution of lead acetate having a con- 12. Method of lead plating an iron or steel article which consists in first bringing the same into contact, without electric current, with a solution of lead acetate having a concentration of at least 35% by weight and then subjecting the article to an electro- 1 re'ntfthen subjecting the article to an elecing a concentration of substantially 10% u plating operation using as an electrolyte a solution of lead acetate of substantially 10% concentration, and keeping the electrolyte in agitation.

13. Method of lead plating an iron or steel article which consists in first bringing the same into contact, without electric current, with a solution of lead acetate having a concentration of at least 35% by weight, then subjecting the article to an electroplating operation using as an electrolyte a solution of lead acetate of substantially 10% concentration, and keeping the electrolyte in agitation, employing for the electrolysis a current not in excess of one to two amperes per square foot of surface to be plated.

14. Method of lead plating an iron or steel article which consists in first bringing the same into contact, without electric current, with a solution of lead acetate having a concentration of at least 35% by Weight, then subjecting the article .to an electroplating operation using as an electrolyte a solution of lead acetate of substantially 10% concentration, and keeping the electrolyte in agitation, employing for the electrolysis a current of substantially one ampere er square foot of surface to ,be plated WhlCll is increased during the electro-plating operation to two amperes per square foot.

15. A metal article covered with a dipped coating and an electrolytic coating, each consisting principally of lead and one coating superposed on the other.

ROBERT JAY SHOEMAKER. 

